1. Field of the Invention
The present invention relates to a disk drive device which performs recording or reproducing to or from a disk-shaped recording medium, and to an unrecorded area detecting method for detecting unrecorded areas on the signal plane of a disk-shaped recording medium with such a disk drive device.
2. Description of the Related Art
With drive devices which perform recording or reproducing actions to or from recording media such as optical disks, magneto-optical disks, etc., an action called xe2x80x9cblank checkxe2x80x9d is performed for confirming whether a given sector (xe2x80x9csectorxe2x80x9d being a unit of data on the recording medium) has already been recorded upon or not.
For example, with drive devices handling WO (Write Once) type disks, data must be written to an unrecorded sector, so a blank check is carried out at the time of recording.
Also, with drive devices handling re-writable disks such as MOs (magneto-optical disks), in the event that an error has occurred at the time of decoding the read data (e.g., sync detection not possible, error correction not possible, etc.), a process for estimating the cause of the error is performed before initiating a read retry, by conducting a blank check of that sector. This is because the cause of the error in decoding and the retry process which should be corresponding are related to the state of the sector, i.e., whether the sector is deemed recorded or unrecorded.
For example, in the event that a read error occurs at the time of write-and-verify (xe2x80x9cwrite-and-verifyxe2x80x9d is an action for reading out recorded data immediately following the recording action of the data, so as to confirm whether or not the data has been correctly recorded), there is a good chance that the action was not a read action and that the write action was not performed appropriately, in the event that the sector is an unrecorded area. On the other hand, in the event that a read error occurs during normal reproduction and the sector is an unrecorded area, the error is a matter of course, and the is not need to perform a read retry action. Also, in the event that the blank check results in the judgement that the section is a recorded area, measures such as changing the read conditions such as the amp gain and so forth should be changed to attempt a retry.
Now, it is considered necessary to perform blank checks for disk drive devices as described above, and the blank checks are conducted as follows for example, in actual practice.
FIG. 8A illustrates a model of a so-called reproducing RF signal waveform obtained by reading information by optical pick-up of a given area on a disk.
With the blank check, first, peak hold or bottom hold for example is performed for this reproducing RF signal, thereby obtaining an envelope waveform EV for the reproducing RF signal. Here, peak hold is performed for the reproducing RF signal.
Then, comparison is made between the level of this envelope waveform EV and a given threshold TH.
Now, in the event that the area (sector) is a recorded area wherein some sort of information has already been recorded, an amplitude waveform corresponding to the information (pits) recorded there is obtained for the reproducing RF signal, meaning that a corresponding level is also obtained for the envelope waveform EV. In this case, the level of the envelope waveform EV is to be greater than the threshold TH, but as long as such a relation is obtained between the level of such an envelope waveform EV and the threshold, judgement is made that the area is not an unrecorded area.
Conversely, in the event that reproduction is attempted for an unrecorded area, there is no information recorded thereto, so hardly any change in amplitude is obtained for the reproduction RF signal. Accordingly, the level of the envelope waveform EV is lower than the threshold TH, as shown in the Figure for example. In the event that such a relation is obtained, judgement is made that the area is an unrecorded area.
However, in actual practice, the reproduction RF signal obtained by reproducing an unrecorded area does not always assume an ideal waveform with almost no amplitude change as shown in FIG. 8A.
That is, as shown in FIG. 8B, there are cases wherein noise amplitude components are superimposed on the actual reproduction RF signals, and amplitudes greater than the reproduction RF signal level corresponding to the actual unrecorded area are obtained due to these amplitude components.
Then, in the event that the amplitude components superimposed as noise onto the reproduction RF signals obtained from the unrecorded area have a certain level or greater, the level of the envelope waveform EV may exceed the threshold TH, and in such cases, erroneous detection may be made that the area has been recorded on even though it is an unrecorded area.
In order to avoid such erroneous detection, the level of the threshold TH may be raised for the case in FIG. 8. That is to say, a threshold TH might be set which is closer to the recorded area side. However, such means are not suitable for actual usage, due to the following reason.
For example, in reality, reproduction RF signal levels obtained corresponding to recorded areas change due to margins of error or offsets in the signal processing systems. Accordingly, setting the threshold TH closer to the recorded area side conversely increases the probability that recorded areas will be erroneously detected as unrecorded areas.
Now, erroneously detecting recorded areas as unrecorded areas may bring about a somewhat fatal error wherein new data is overwritten in a recorded area in subsequent processing.
In light of this, there is the pragmatic need to set the threshold as a value as close as possible to a reproduction RF signal level corresponding to the unrecorded area.
Accordingly, conducting testing for a given device model in order to obtain a threshold which is as close as possible to a reproduction RF signal level corresponding to unrecorded areas and which is highly reliable, and setting this threshold for each device being shipped from the production line, is realistic.
However, causes for the noise component of the reproduction RF signals as described above include for example noise generated by detectors and signal processing system in optical pickups, cross-talk of data recorded on the track where detection was performed, etc., but such noise quantity is not necessarily the same for all devices of the same model, since there are irregularities in the optical pickups for each disk drive device, and in offset such as the gain of the signal processing system. Accordingly, obtaining a threshold common to each device with high reliability in a sure manner is difficult.
Accordingly, in light of the above problems, it is an object of the present invention to allow an appropriate threshold for blank checks to be set regardless of irregularities in parts from one device to another, i.e., regardless of differences in the noise levels superimposed on the reproduction RF signals from one device to another, thereby improving the reliability of blank checking.
To this end, the disk drive device is configured as follows.
The disk drive device comprises:
information writing/reading means for recording or reproducing information by irradiating laser beams onto a signal plane of a disk-shaped recording medium;
unrecorded area detecting means for detecting unrecorded areas on the signal plane, based on the results of comparing reproduction signal levels from the information writing/reading means with a predetermined threshold; and
threshold adjusting means for executing adjustment actions for setting the threshold;
The threshold adjusting means comprise:
action control means for controlling the information writing/reading means so that a reproducing action is performed regarding a certain adjusting area which is an unrecorded area;
threshold variating means for changing the adjustment threshold at the time of performing reproducing actions regarding the adjusting area; and
threshold determining means for making comparison for each changed adjustment threshold with reproduction signal levels, and determining the threshold based on the comparison results.
Also, the unrecorded area detecting method is configured as follows.
The unrecorded area detecting method is applied to a disk drive apparatus for recording or reproducing information by irradiating laser beams onto a signal plane of a disk-shaped recording medium, wherein execution of:
an unrecorded area detecting process for detecting unrecorded areas on the signal plane based on the results of comparing reproduction signal levels with a predetermined threshold; and
a threshold adjusting process for setting the threshold are enabled.
The threshold adjusting process comprises:
an action control process for executing control so that a reproducing action is performed regarding a certain adjusting area which is an unrecorded area;
a threshold variating process for changing the adjustment threshold at the time of performing reproducing actions regarding the adjusting area; and
a threshold determining process for making comparison for each changed adjustment threshold with reproduction signal levels, and determining the threshold based on the comparison results.
According to the above configuration, the setting of this threshold is performed by performing reproduction regarding an adjustment area serving as an unrecorded area on the disk-shaped recording medium while varying the adjusting threshold, under the assumption that the arrangement has the functions of detecting an unrecorded area by comparing a reproduction signal level obtained by conducting reproduction of the disk-shaped recording medium with a threshold. Then, the threshold actually used for detection of unrecorded areas is set based on the comparison results between the adjusting threshold and the reproduction RF signal. This means that a threshold appropriate for each device is automatically set, regardless of conditions such as differences in noise levels superimposed on reproduction signals, from one device to another.